The present invention relates to a traction apparatus for moving apart two parts of a bone, in particular for bone extension or to bridge a bone gap, comprising a medullary pin which can be introduced into the medullary space of a bone and which has two parts respectively securable to one of the two bone parts and moveable axially apart, a drive unit which drives a drive shaft and a device for converting the rotational movement of the drive shaft into a relative axial movement of the two parts of the medullary pin.
The use of a medullary pin as part of such a traction apparatus is known from document DE 39 21 972 C2. This apparatus serves in particular for the extension of tubular bones or the bridging of defects after comminuted fractures, or an inflammatory bone process or after the removal of tumors in the area of longer tubular bones. This known apparatus already has considerable advantages in comparison with external traction apparatuses in which the bone parts are connected outwardly through the skin to an adjustable frame, since through this a continuous danger of infection is present due to the entry of germs and also an unfavorable application of force is present.
The manner of operation of the known medullary pin is such that by moving the two parts of the medullary pin apart from one another the two parts of the bone can be moved slowly apart from one another, with the gap which thereby forms between the two bone ends continuously being bridged by newly forming bone substance as a result of the slow advance. In this manner bone can not only be extended in that bones are separated and subsequently drawn apart after drilling and insertion of the medullary pin into the medullary space, but rather bone gaps can also be bridged in that a bone piece separated from a bone end adjacent to the gap is moved from the one end of the gap to the other. Accordingly the end of a bone stub, i.e. a bone with a missing bone end, can also be extended.
Important in an apparatus of the initially named kind is that the movement of the bone parts apart from another takes place slowly in order to provide adequate time for the formation of bone substance and for the adaptation of the surrounding tissue.